1. Field of the Invention
The present invention relates to an apparatus and method for transferring objects in a processing system. More specifically, the present invention relates to a robot assembly having a multiple sided robot blade which can support one or more substrates.
2. Background of the Related Art
Modern semiconductor processing systems typically process a large number of substrates by moving the substrates between a series of process chambers or enclosures using a robot. To increase the throughput rates of substrates, the trend is to increase the speeds at which substrates are moved in the system. However, increased speeds add complexity to the substrate handling systems. Increased speeds have decreased the allowable tolerances necessary to maintain repeatability because precise movement is needed to avoid damaging the substrate or the films formed thereon as the substrate is moved between the process chambers or enclosures using the robot.
One type of system used in substrate processing is a chemical mechanical polishing (CMP) system used to polish a substrate surface to remove high topography, surface defects, scratches, or embedded particles. FIG. 1 is a schematic perspective view of one CMP system known as a Mirra(copyright) CMP system available from Applied Materials, Inc. of Santa Clara, Calif., which is shown and described in U.S. Pat. No. 5,738,574, incorporated herein by reference. The system 2 includes a loading station 4 and three polishing stations 6 having polishing and/or rinsing pads 8 disposed therein. A rotatable multi-head carousel 10 having four polishing heads 12 is mounted above the stations and indexes the heads from station to station. The loading station 4 is supplied by a front-end substrate transfer region 14 disposed adjacent to the CMP system and is considered a part of the CMP system, although the transfer region 14 may be a separate component. The loading station 4 includes a pedestal 16 on which a substrate is supported following delivery by an overhead track robot 18 prior to and after processing in the polishing stations 6. Vertically aligned substrate(s) 20 are held in cassette(s) 22 disposed in a fluid in a load tank 24.
Generally, an overhead track robot 18 includes a downwardly extending blade support arm 28, also known as a shoulder. A blade 26 is attached to the blade support arm at a pivot joint 30, typically referred to as a wrist. The track robot 18 is capable of operating the blade support arm in three directions: in a linear direction along an X-axis across the front of the system, in a vertical direction along a Z-axis, and in a rotational direction about the Z-axis. Additionally, the blade 26 is capable of rotating about pivot joint 30 between a substantially horizontal position and a substantially vertical position. The blade 26 typically includes a vacuum port (not shown) for holding a substrate 20 to the blade during transfer within the system 2.
FIG. 2 is a cross sectional schematic view of the overhead track robot 18, showing details of the robot components. A blade support arm 28 is vertically disposed below a carriage 32. The carriage 32 is attached to a drive belt 34 which is supported between two sheaves 36, 38. A motor 40 having a worm gear 42 is mounted on the carriage 32 and engages a mating gear 44 mounted on the support arm 28. The blade support arm 28 supports a support column 60 that is connected to the pivot joint 30. The pivot joint 30 includes a first portion 46 connected to the blade support arm 28, a second portion 48 connected to a blade 26, and a pivot element 50 pivotally connecting the first portion 46 with the second portion 48 of the pivot joint 30. The pivot joint 30 allows the blade 26 to rotate at a pivot axis 52 between a horizontal and a vertical position. The blade 26 is a single-sided blade, i.e., the blade has one substrate supporting surface that is used to support the substrate during retrieval and delivery of a substrate 20 from and to the various stations. The carriage 32 houses a motor 54 having a worm gear 56 which passes through a worm nut 58 attached to the support column 60. The blade support arm 28 houses a motor 62 which is attached to a drive shaft 64 and a worm gear 66. The worm gear 66 engages a mating gear 68 on the pivot joint 30. The blade 26 is attached by screws (not shown) to the pivot joint 30.
The blade support arm 28 rotates about the Z-axis 70 when the motor 40 rotates the worm gear 42 which in turn rotates the mating gear 44 connected to the blade support arm. In the typical system, the pivot axis 52 is offset from the Z-axis 70 to enable use of a shorter blade 26 and consequently reduce blade deflection when extended horizontally in the system 2 on delivery and retrieval of a substrate 20. The worm nut 58 rises and lowers on the worm gear 56 as the motor 54 rotates the worm gear 56, thus raising and lowering the support column 60 attached thereto. To rotate the pivot joint 30 about the pivot axis 52, the motor 62 rotates the drive shaft 64 which causes the worm gear 66 to rotate. Rotation of the worm gear 66 causes the mating gear 68 to rotate, thus rotating the second portion 48 of the pivot joint 30 and the blade 26 attached thereto.
Typically, in loading the substrate 20 into the system 2, the robot 18 rotates the blade 26 into a vertical position, aligns the blade 26 with the substrate, lowers the blade 26 into an adjacent position with the substrate 20, and vacuum chucks a substrate 20 on a substrate supporting surface of the blade 26. A vacuum provided to a port on the blade supplies a vacuum to hold the substrate 20 to the supporting surface of the blade 26 so that when the blade is raised vertically, the substrate remains supported by the blade in the vertical position. The robot 18 then rotates the blade 26 about the pivot joint 30 into a substantially horizontal position, moves in the X-direction toward the loading station 4 rotates the blade about the Z-axis 70, aligns the blade with a loading station 4, and delivers the substrate to the loading station. The loading station pedestal 16 raises to engage the substrate 20 and lowers the substrate below the blade 26 so that the blade 26 can retract out of the loading station 4. One of the heads 12 indexes above the pedestal 16, the pedestal 16 raises the substrate 20 into contact with the head, the head chucks the substrate and indexes to a polishing station 6 for processing. After processing at the station(s), the substrate 20 is returned to the loading station 4. The robot 18 aligns the robot blade 26 with the loading station 4 to retrieve the processed substrate, retrieves the processed substrate, traverses the X-axis back into an unloading position at the load tank 24, and returns the substrate 20 to the load tank 24. The robot then loads another unprocessed substrate and delivers the substrate to the loading station 4.
One problem with this conventional design and process is that the system may sit idle while awaiting retrieval of an unprocessed substrate following removal of a processed substrate. The time required for the robot to cycle between a processed substrate and an unprocessed substrate is typically referred to as the xe2x80x9cswapxe2x80x9d time. In the system referenced in FIG. 1, the swap time includes the time required to retrieve and place a processed substrate in the load tank and retrieve and deliver an unprocessed substrate to the loading station.
There remains a need for a system and method that can reduce the swap time required to pick up a processed substrate and position an unprocessed substrate for processing in the system.
The present invention generally provides a processing system having a robot assembly which includes a multiple sided robot blade that can support a substrate on at least two sides thereof and associated methods to transfer one or more substrates in a processing system. An unprocessed substrate can be supported on the blade while a processed substrate is retrieved from a location to which the unprocessed substrate is to be delivered. The processing throughput rate is increased by reducing the movements required by the robot to exchange processed substrates and unprocessed substrates, thus decreasing the swap time.
In one aspect, the invention provides a substrate processing system, comprising an enclosure, a robot as least partially disposed within the enclosure, and a multiple sided robot blade attached to the robot and adapted to support substrates on at least two surfaces thereof. The robot can include a blade support arm connected to a drive mechanism, a pivot joint connected to the blade support arm, a two sided blade connected to the pivot joint, and associated actuators and controllers. In another aspect, the invention provides a robot blade for a substrate processing system, comprising a first and a second substrate supporting surface on opposed faces of the blade.
In another aspect, the invention provides a method for transferring substrates in a processing system, comprising supporting a first substrate on a first substrate supporting surface of a robot blade, retrieving a second substrate on a second substrate supporting surface of the robot blade from the system, and delivering the first substrate supported on the first substrate supporting surface to the system while supporting the second substrate on the second substrate supporting surface. In another aspect, the invention provides a method of transferring substrates in a processing system using a robot, comprising retrieving a first substrate from a first location and supporting the first substrate on a first substrate supporting surface of a robot blade, positioning the robot blade to retrieve a second substrate from a second location, retrieving the second substrate from the second location and supporting the second substrate on a second substrate supporting surface of the blade, delivering the first substrate to the second location, and delivering the second substrate to another location in the system.